Gonzalez Rosario, Alexa M.

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    Production of sugars, lignin and platform molecules from biomass residues feedstocks using Brønsted acid catalysts in polar aprotic solvents
    (2023-07-07) Gonzalez Rosario, Alexa M.; Cardona Martinez, Nelson; College of Engineering; PagĂ¡n Torres, Yomaira J.; Flores Mangual, Mario; Abelleira MartĂ­nez, Oscar J.; Department of Chemical Engineering; Morell Cruz, Luis
    We studied the catalytic conversion of the wood of Spathodea campanulata (African tulip tree), Albizia procera, and Leucaena leucocephala for the production of sugars using 0.05 and 0.5 wt% of H2SO4 in a mixture of water and γ-valerolactone. We obtained total yields up to 100, 100 and 74 wt% for African tulip tree, Albizia procera and Leucaena leucocephala, respectively. We found that the amorphous cellulose phase in these residues had a lower thermal stability than the hemicellulose and the crystalline phase of cellulose. Using a reacting bed flow reactor with 0.05 wt% of H2SO4 in a solution of 70% GVL and 30% water using a temperature ramp of 0.5 K/min (430 to 490 K) we found a 66 wt% yield towards C6 sugars for African tulip tree. We also studied how the crystallinity and particle size of cellulose affects its reactivity. We studied the effect on the cellulose conversion into levoglucosenone. We found that a decrease in the cellulose crystallinity rendered the cellulose more reactive but can also promote the degradation of levoglucosan and levoglucosenone. In addition, we studied the hydrolysis of cellulose. The amorphous phase of cellulose reacted at lower temperatures suggesting lower thermal stability. We presented a semi-batch process to produce levoglucosenone from cellulose using low concentrations of Brønsted acid catalysts in polar aprotic solvents. The TOF for the reaction increased with a decrease in the solvent basicity. High reaction temperatures had a negative effect on the LGO yield and promoted the formation of degradation products. At 430 K, using H2SO4 in GVL we obtained an LGO yield of 24 wt% and an LGA yield of 34 wt%. We studied the conversion of LGA into LGO using propyl sulfonic SBA-15 (PS-SBA-15) in a flow reactor using GVL. PS-SBA-15 is a functionalized mesoporous silica and a solid Brønsted acid catalyst. The maximum selectivity towards LGO was 67% at 57% conversion of LGA. The water formed during the reaction did not affect the catalyst activity appreciably but modified the products distribution. The PS-SBA-15 catalyst deactivated with time on stream (TOS). After 6 h TOS, the catalyst lost 66% of its initial activity. A series of unsuccessful catalyst regeneration treatments suggests that the loss in catalyst activity may be because of surface reaction site blockage or loss of the SBA-15 structure due to the interaction with water.